The invention relates to a monolithic, non-planar ring laser. In particular, this invention is directed to a laser capable of generating high-power laser pulses in single-frequency operation using active or passive Q-switching.
U.S. Pat. No. 4,797,896 to Kane describes a monolithic, non-planar ring laser operated in continuous, single-frequency, which however incurs the drawback of not allowing pulse operation, so that high peak powers are impossible.
A monolithic, non-planar ring laser Q-switched by an antiresonant saturable Fabry-Perot absorber is known from the "Optics Letters" vol. 20, #9, pp 1020-1022. This laser however suffers from the drawback of allowing only passive Q-switching. High pulse-repetition rates in the MHz range reduce peak powers to a few watts. Moreover the manufacture of such antiresonant saturable Fabry-Perot absorbers is costly.
A Q-switched microchip laser with a resonator-internal, saturable absorber or with Q-switching Cr, Nd:YAG solid lasers of which the active medium suffers saturable losses at lasing transition is known from the "Optics Letters" vol. 19, #18, pp 1427-1429 and vol. 18, #3, pp 203-204 as well as vol. 18, #17, pp 1418-1419. These lasers known from said publications preclude high average powers in single-frequency operation.
The European patent document EP 0,272,912 describes Q-switching of conventional solid lasers by acousto-optic or separately saturable absorbers in the laser resonator. This design incurs the drawback of a discrete construction, entailing stability and efficiency degradation. Single-frequency operation is possible only at high equipment cost or only at low powers.
The object of the present invention is to so design a ring laser of the initially cited species that it will implement high-power laser pulses in highly stable single-frequency operation. Moreover compactness is desired.
The non-planar monolithic ring laser of the invention by means of active or passive Q-switching allows efficiently generating short, high-power laser pulses in high-stability frequency operation. By combining pulse repetition rates in the kHz range and a short resonator length, nanosecond pulses with peak powers in the kW range are achieved.
Compactness, high stability and reliability are achieved by means of the laser's monolithic structure. The (longitudinal) excitation of the invention using a diode laser allows high total electro-optic efficiency. Mode-selective pumping constrains the emission of the transverse fundamental mode with diffraction-determined beam quality. On the whole the optic excitation can be carried out with up to four diode lasers using a coupling mirror of the ring laser.